Experimental reactor physics "Past, present and future"; Towards establishment of safety basis in next generation, 5; Status and outlook of thermal reactor physics experiments in JAEA

Tonoike, Kotaro 

Almost 50 years have passed since the former Japan Atomic Energy Research Institute (JAERI) started the operation of the first critical assembly (CA). Since then, CAs of various types have been served for the experimental research of the reactor physics in the former JAERI, the former Power Reactor and Nuclear Fuel Development Corporation, and current Japan Atomic Energy Agency (JAEA), where the nuclear development history of Japan can be seen. From the view point of the power reactor development, the light water reactor (LWR) was not an obvious option in the early days while all nuclear power plants (NPPs) in Japan are LWRs. Concepts of the graphite reactor and the heavy water reactor were also studied with CAs, where possibility of the breeding with the thermal reactors was investigated as well. Only for the LWR development, various research activities have been conducted for the core and fuel design advancement of NPPs, the reactor of a nuclear propulsion ship, the high conversion reactor, etc. The criticality safety (CS) is an important research field, too, which is prevention of the criticality while the power reactor development is the research how to achieve and maintain the criticality and how to burn fuel well. The CS and the critical experiments are inseparable because the basic way of CS is the critical mass measurement of nuclear material and the enough mass reduction for the nuclear material handling in the safe subcritical condition. History from the past to the present is introduced focusing on critical experiments of the thermal reactor system conducted in JAEA. Its future perspective is also mentioned.